Whale Sharks now considered Endangered by IUCN

Major contemporary threats to Whale Sharks include fisheries catches, bycatch in nets, and vessel strikes. Other threats affect Whale Shark on local or regional scales.

Whale Sharks are presently fished in several locations. In southern China, large-scale commercial take of Whale Sharks appears to be increasing (Li et al. 2012). Although Whale Sharks are not necessarily targeted, they are routinely captured and retained when sighted (Li et al. 2012). A small-scale opportunistic fishery for Whale Sharks is also present in Oman (D. Robinson, pers. comm).

Whale Sharks have previously been targeted in large-scale fisheries from India, the Philippines and Taiwan, with hundreds of sharks caught annually in each country until species-level protections were implemented (Rowat and Brooks 2012). A smaller directed fishery occurred in the Maldives until Whale Sharks were protected in 1995 (Anderson and Ahmed 1993). Broader-scale subpopulation reduction caused by these fisheries was raised as a possible driver of declining sightings in Thailand (Theberge and Dearden 2006) and Western Australia (Bradshaw et al. 2008). Occasional directed catch or bycatch of Whale Sharks has been documented from many of their range states, particularly where large-mesh gillnets are in common use (Rowat and Brooks 2012).

Tuna are often associated with Whale Sharks, and tuna purse-seine fisheries often use Whale Sharks as an indicator of tuna presence, even setting nets around the sharks (Capietto et al. 2014). Direct mortality in purse-seine fisheries appears to generally be low, recorded as 0.91% (one of 107) and 2.56% (one of 38) of sharks where fate was reported by observers in the Atlantic and Indian Oceans, respectively (Capietto et al. 2014). However, estimated mortality rates in the Western Central Pacific purse-seine fishery were higher: 12% for 2007–2009 and 5% in 2010. This extrapolated to a total mortality of 56 sharks in 2009 and 19 in 2010 (Harley et al. 2013). Observer reports on release condition from this region from 2010–2014 were generally consistent, with 50–60% of encircled sharks released alive, 5–10% dying and 30–40% of status unknown (Clarke 2015). Assuming a poor outcome for the latter category, potential mortalities in 2014 range from a minimum of 11 to 42, with a higher number possible depending on longer-term survival of the sharks released alive (Clarke 2015). Available data on the number of Whale Sharks caught are likely to underestimate total catch (Clarke 2015). The longer-term survivorship of Whale Sharks released from nets has not been examined at this stage. Common release practices, such as being lifted or towed by the caudal peduncle, are likely to cause stress, injury and possibly death to the sharks.

Shipping lanes, where they are placed close to Whale Shark feeding areas, can create a serious risk of vessel strikes. Whale Sharks routinely feed at the surface (Motta et al. 2010, Gleiss et al. 2013), and propeller injuries are commonly recorded during monitoring programs (Rowat et al. 2006, Speed et al. 2008, Fox et al. 2013). While mortality events are seldom reported in the contemporary scientific literature, they were often noted from slower-moving vessels in the past (Gudger 1941). It is likely that fast-moving, large ships do not register or report impacts, and as Whale Sharks will typically sink upon death, these are unlikely to be documented (Speed et al. 2008). Areas where Whale Sharks appear to be at particular risk include the Mesoamerican reef countries in the Western Caribbean (Graham 2007, R. de la Parra-Venegas pers. comm.) and Gulf states (D. Robinson pers. comm.), where a high frequency of serious propeller injuries are observed during monitoring.

Inappropriate tourism may be an indirect threat to Whale Shark in some circumstances (for example from interference, crowding or provisioning). Marine pollution events occurring in Whale Shark hotspots, such as the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 (Hoffmayer et al. 2005, McKinney et al. 2012), may result in mortality or displacement from preferred habitats. These more local threats, as well as potential future concerns such as climate change impacts (Sequiera et al. 2014), should be closely monitored.

Read more about the Whale Shark on the IUNC’s website